There are five kinds of desert wilderness: the desert mountains, the rocky plateau, the sand dunes, the salt marshes, and the broken or deserted terrain known as the gebel or wadi. Each type of desert terrain has its own characteristics and each hinders easy travel or transport over the desert area. Navigation, the actual planning of a trip across the desert, is difficult because there are few landmarks plus intense heat causes optical illusions to the distant horizon. All desert terrain has sparse cover and the threat of exposure to the elements lasts both day and night.
The mountain ranges are usually scattered from one another with other forms of desert in between. Many have high, although gentle slopes to the desert peaks which can cause instant floods when the rain abruptly flows down the mountain to the flat land below. Most of the deserts in the US have desert mountains that are several thousand feet elevation at the lowest valley crossing. Due to the flash flood nature of the rain on the desert, the canyons between the mountains are quite steep and narrow. It is not uncommon to attempt to cross a range in a valley only to find the valley closes with only cliff walls ahead.
Rocky plateaus are steep walled with high flat table-like plateaus with little vegetation and few broken rocks. Like the mountain area, the rain comes rarely and in flash floods, the surfaces of the sidewalls of the plateau often wash into the valley and color the ground for miles around. In the US, native Indians have used the sidewalls for housing at times. Generally, it is not safe to establish a colony near the base of a plateau on the flat land below. These will flood, and canyons in the plateau formation will be steep.
Sand Dune Areas
Sandy areas or sand dunes are often extensive areas where the sand runs for miles and miles, and the size of the sand is very fine. The areas are often subject to heavy winds at the time of the change of the seasons, and the dunes may change their whole configuration three or four times in a calendar year. This fact alone makes it very hard to navigate up the dunes, as they are constantly changing with no points of reference over periods as short as a week. Your ability to traverse the sand dunes will depend on the texture of the sand. Try both the windward and leeward sides to find which is easiest on a particular expanse of dunes.
In areas of the desert below sea level, or in areas where flash floods accumulate periodically in lakes, the desert will form large salt marshes. These are flat, hard, and very hot to traverse. This type of desert is particularly prone to produce the vision effect called ‘mirage’. This makes navigation difficult because you are easily fooled into changing direction just to continue a straight course. The areas reflect the sun’s UV rays, so get out your sunscreen.
Wadi and Gabel
The areas where you can see the effects of the flash flood erosion are called the wadi areas of the desert. The effect can go from six inch high erosion oaths to three thousand feet wide canyons where the water has literally carved the desert into a deep v-shaped canyon. The Wadi soon becomes a Gabel where the canyons twist and turn like a maze with multiple paths turning at near angles to the next. It is easy to get lost.